Field of the Invention
The present invention relates to a lens barrel for an optical apparatus, such as a video camera and a digital still camera.
Description of the Related Art
A conventional lens barrel having a so-called manual focus (“MF”) function detects a rotation of an operating ring using electric means, and electrically drives a focusing lens in accordance with the rotation.
Japanese Patent Laid-Open No. 2012-255899 discloses a lens barrel configured to detect a rotation amount and a rotation direction of a rotational operation unit based on a detection signal obtained from a pair of photo-interrupters that detect light passing through a plurality of slits (notches) provided at regular intervals in the circumference direction of the rotational operation unit. The lens barrel disclosed in JP 2012-255899 rotates a screw through a stepping motor in accordance with the rotation information of the rotational operation unit containing, for example, the rotated direction and the rotation amount, and realizes a manual focusing mode (MF function) by following the movement of a nut engaged with the screw.
The lens barrel disclosed in JP 2012-255899 detects the rotation of the rotational operation unit using a noncontact type structure with the pair of photo-interrupters for the MF function. The photo-interrupter consumes a comparatively large amount of current. In addition, the rotation of the rotational operation unit cannot be detected when none of the outputs of the pair of the photo-interrupters change, and it is thus difficult to improve the rotation detecting resolution.